Pressure cell experiments composites

On the same topic of DMFC performance with supported vs. unsupported catalysts Smotkin and co-workers concluded that at 363 Kthe supported PtRu (1 1) catalyst with a toad of 0.46 mg cm performed as welt as an unsupported PtRu (1 1) with over four times higher load, i.e., 2 mg cm [266]. It is likely that these differences between various studies are related not only to the intrinsic activity of the respective anode catalys layers but also to the manufacturing procedures such as catalyst layer preparation and application techniques, MEA hot pressing conditions (temperature, pressure and time), presence or absence of other binders (such as PTFE) and fuel cell compression. All these MEA manufacturing variables can affect, in a poorly understood manner at present, the structure, morphology and composition of the catalyst layer in the operating fuel cell. Therefore, in fuel cell experiments it is difficult to isolate the truly physico-chemical effect of the support on the catalytic activity. 

Besides temperature and polymer composition, pressure is a third parameter needed to completely determine the thermodynamic equilibrium state of a binary mixture. So far, only a few systematic SANS studies exist for polymer blends in external pressure fields [34-41]. Those experiments were also performed in our laboratory for which a temperature-pressure cell was developed for in-situ investigations allowing pressure and temperature fields between 0.1 < P(MPa) < 200 and - 20 < T(°C) < 200, respectively. A temperature control better than 0.01 K allowed also precise exploration of thermal composition fluctuations near the critical point [34]. 

Factors may be classified as quantitative when they take particular values, e.g. concentration or temperature, or qualitative when their presence or absence is of interest. As mentioned previously, for an LC-MS experiment the factors could include the composition of the mobile phase employed, its pH and flow rate [3], the nature and concentration of any mobile-phase additive, e.g. buffer or ion-pair reagent, the make-up of the solution in which the sample is injected [4], the ionization technique, spray voltage for electrospray, nebulizer temperature for APCI, nebulizing gas pressure, mass spectrometer source temperature, cone voltage in the mass spectrometer source, and the nature and pressure of gas in the collision cell if MS-MS is employed. For quantification, the assessment of results is likely to be on the basis of the selectivity and sensitivity of the analysis, i.e. the chromatographic separation and the maximum production of molecular species or product ions if MS-MS is employed. 

The addition of H2O and CO2 to the fuel gas modifies the equilibrium gas composition so that the formation of CH4 is not favored. Carbon deposition can be reduced by increasing the partial pressure of H2O in the gas stream. The measurements (20) on 10 cm x 10 cm cells at 650°C using simulated gasified coal GF-1 (38% H2/56% CO/6% CO2) at 10 atm showed that only a small amount of CH4 is formed. At open circuit, 1.4 vol% CH4 (dry gas basis) was detected, and at fuel utilizations of 50 to 85%, 1.2 to 0.5% CH4 was measured. The experiments with a high CO fuel gas (GF-1) at 10 atmospheres and humidified at 163°C showed no indication of carbon deposition in a subscale MCFC. These studies indicated that CH4 formation and carbon deposition at the anodes in an MCFC operating on coal-derived fuels can be controlled, and under these conditions, the side reactions would have little influence on power plant efficiency. 

Deaton and Frost (1946) suggested the same apparatus could be used for conditions below the ice point. In these experiments, gas was first bubbled through water above 273 K, to form a honeycomb mass of hydrate. Then free water was drained before the cell was cooled below the ice point. After the temperature was stabilized, gas was removed in small increments until a region of constant pressure was obtained, which indicated dissociation of the hydrate phase. Deaton and Frost used this procedure only for equilibria of simple hydrates, since the hydrated mass of guest mixtures was not constrained to be of uniform composition, and consequently would have decomposed at different pressures. 

In the case of the measurement of the diffusivity in the p-xylene + o-xylene counterdiffusion experiment, the sample was initially saturated with a stream of p-xylene at a partial pressure of 6.7 Pa then, to this stream of carrier gas plus p-xylene, the carrier gas saturated with o-xylene was admitted, to finally obtain the same partial pressure, 6.7 Pa, for both hydrocarbons. The composition of the final hydrocarbon mixture, that is, the gas phase concentration of p-(cp x) and o-(c0.x) xylene, obtained was checked with a gas chromatograph (FISONS 8000) coupled to the gas outlet of the IR cell (see Figure 5.34). The gas phase concentration, for p-(cp x) and o-xylene (c x) in the fed mixture of the counterdiffusion experiment was the same cp x [%] = c0 x [%] = 50 [%] [90], If Figure 5.34, the uptake curves corresponding to the counterdiffusion kinetics of para + ortho xylene in H-ZSM-11 at 375 K and 400 K are shown [90],... 

Basic experiments were carried out with an extractor in analytical scale (SFE-703, DIONEX). For a typical experiment the extraction cells (10 ml internal volume) were fully filled with a homogeneous mixture of the flame retardent and the inert MgS04 and placed into the oven chamber of the extractor. After reaching the desired extraction conditions (pressures of 250 to 500 bar and temperatures of 60, 80 or 100 °C) the samples were extracted for 45 min. The extracted components were analysed by gravimetric, spectroscopic and/or chromatographic methods (IR, GC-MSD). Further experiments were made with realistic brominated ABS composites (granulated composites) in analytical scale and also with an extraction autoclave in laboratary scale (500 ml internal volume). 

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